1. Technical Field
The present invention relates to curved liquid-crystal display devices and to backlights used for curved liquid-crystal display devices.
2. Description of the Related Art
In recent years, as liquid crystal display devices have come to be used as display devices of television receivers, the screens of such liquid crystal display devices have become increasingly bigger. But a problem with increasingly larger television LCD screens is that the viewing angle difference between the viewing angle when the viewer views the center portion of the screen and the viewing angle when the viewer views the left and right edges of the screen increases (throughout this specification, the technical term “viewing angle” is defined as the angle between the line of sight of the viewer viewing the screen and the tangent to the intersection between the line of sight and the observed screen surface, and the difference between the center and left/right edge viewing angles is defined as and used to mean the “viewing angle difference”).
Furthermore, another problem with large-scale television LCD screens is that glare off the screens also increases. The problem of difference in viewing angle can be corrected by curving the screen into a concave shape.
However, even when the viewing angle difference is improved by a liquid-crystal panel with a concavely curved screen (referred to as “concavely curved liquid-crystal panel” below), when using a backlight with the same structure as that of a conventional flat liquid-crystal panel for such a concavely curved liquid-crystal panel, there is the problem that the uniformity of light that is emitted from the light source inside the backlight is lost in particular at the peripheral edges of the concavely curved liquid-crystal panel. As a result, the image quality of the concavely curved liquid-crystal panel becomes lower than that of the screen of a conventional flat liquid-crystal display device.
As a countermeasure for solving this problem and using the backlight for a conventional flat liquid-crystal panel is to enlarge the space in which the light source of the backlight is arranged.
This countermeasure will be explained with reference to FIG. 8.
FIG. 8A is a diagrammatic cross-sectional view illustrating the relation between the line of sight of a viewer observing the two edges of a concavely curved liquid-crystal panel and the horizontal width of the backlight. FIG. 8B is a diagrammatic cross-sectional view illustrating the relation between the line of sight of a viewer observing the two edges of a liquid-crystal panel and the horizontal width of the backlight for the case that also the backlight is concavely curved.
At the edge portion 802 of the concavely curved liquid-crystal panel in FIG. 8A, there are no light rays of direct light reaching the eye of the viewer after from the backlight passing through the edge portion 802. Therefore, the brightness of the screen at the corner portion 802 becomes lower.
If the horizontal width w3 of the backlight is broadened to w4 as a countermeasure, then it is possible to attain light rays 801 of direct light reaching the eye of the viewer after passing from the backlight through the edge portion 802 and thus to improve the brightness at the edge portion 802.
However, this countermeasure makes the outer shape of the liquid-crystal display device bigger, and thus stands in the way of fulfilling the demand of making the display device slimmer. On the other hand, as shown in FIG. 8B, if the backlight itself is provided with a concavely curved shape matching the shape of the concavely curved liquid-crystal panel, then it is possible to attain light rays 801 of direct light reaching the eye of the viewer from the curved backlight without broadening the horizontal width of the backlight, and thus to improve the brightness at the edge portion 802.
(See JP 2005-150056A.)